linux-kernel - Re: [PATCH 1/3] ioctl: generic ioctl dispatcher

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Date:	Mon, 29 Sep 2008 19:16:35 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, viro@...IV.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] ioctl: generic ioctl dispatcher

Avi Kivity <avi@...hat.com> writes:

> +/**
> + * dispatch_ioctl - dispatch to an ioctl handler based on ioctl number
> + * @inode:	inode to invoke ioctl method on
> + * @filp:	open file to invoke ioctl method on
> + * @cmd:	ioctl command to execute
> + * @arg:	command-specific argument for ioctl
> + * @handlers:	list of potential handlers for @cmd; null terminated;
> + *              place frequently used cmds first
> + * @fallback:   optional function to call if @cmd not found in @handlers
> + *
> + * Locates and calls ioctl handler in @handlers; if none exist, calls
> + * @fallback; if that does not exist, return -ENOTTY.
> + */
> +long dispatch_ioctl(struct inode *inode, struct file *filp,
> +		    unsigned cmd, unsigned long arg,
> +		    const struct ioctl_handler *handlers,
> +		    long (*fallback)(const struct ioctl_arg *arg))

The basic idea is good, but i don't like the proliferation of callbacks,
which tends to make complicated code and is ugly for simple code
(which a lot of ioctls are)

How about you make it return an number that can index a switch() instead?
Then everything could be still kept in the same function.

-Andi
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